Yep, definitely a security issue. I would have shot the intruder dead, therefore making him very easy to locate. Not sure if a concealed weapons permit is a valid option for your friend, and regardless it won't help the current situation, but it does provide a feeling of security in case that were to happen again.
Ouch. I'm glad I wasn't coming into your room last year when Mercure gave me a key card to an already occupied room in Berlin.
I've noticed that quite a few European hotels don't have a secondary locking system from the inside. I find that to be an invaluable aid in keeping this from happening.